1. Field of the Invention
The present invention relates to a seek method and an apparatus using a stepping motor, which controls a seek operation of a head carriage or the like using a stepping motor.
2. Description of Related Art
Typical conventional seek methods using a stepping motor include the one-phase excitation, two-phase excitation, and alternation of the one-phase excitation with two-phase excitation. Since the present invention is directed to an improvement in the two-phase excitation, the conventional two phase excitation will be explained with reference to FIGS. 1 and 2 to help understanding of the present invention. FIG. 1 is a block diagram showing a conventional two-phase excitation circuit, and FIG. 2 is a flowchart of major signals of the circuit of FIG. 1. This configuration is widely used in an FDD (Floppy Disk Drive).
In FIGS. 1 and 2, the reference numeral 1 designates a step pulse train transferred from a host system, and 2 designates a direction signal also transferred from the host system. The step pulse train 1 and the direction signal 2 are both inputted to a step-control circuit 3, which generates two-phase exciting signals 7-10 on the basis of the two input signals 1 and 2. The two-phase exciting signals 7-10 are supplied to a drive circuit 5, which produces drive signals 15-18 in response to the two-phase exciting signals 7-10. The drive signals 15-18 correspond to the two-phase exciting signals 7-10, respectively, and are supplied to a stepping motor 6.
The conventional excitation methods, however, have the following drawbacks:
(1) Drawbacks of the one-phase excitation are small torque producing ability, oscillation involved in stepping, and rough positioning accuracy.
(2) Drawbacks of the two-phase excitation are loud seek noise, and large current consumption. (Its advantages are large torque producing ability, and high positioning accuracy).
(3) Drawbacks of the alternation of the two-phase excitation with one-phase excitation are those of the two-phase excitation and the one-phase excitation, which occur alternately for each step.